• State TI Thinks Resolved
  • Locked Locked
  • Replies 13 replies
  • Answers 6 answers
  • Subscribers 64 subscribers
  • Views 457 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS544C25: VSET Eeprom ISP Programming

JDJ
Expert 3511 points
Part Number: TPS544C25

I use two TPS544C25RVFR DC-DC controllers on this design - one for 1.1V DDR5 VDD and one for 0.82V CXL controller Vcore. I used WBDesign online tools for these two circuit designs. They have similar circuit but different value for comments in FB, COMP and RT circuit due to loading and voltage different.

They have different usage for Vset per WBDesign online tools generated circuit:

  • Vset is used for 1.1V DDR5 VDD – Rbootup = 133K 1%
  • Vset is not used for 0.82V CXL controller Vcore – it is pulled up to V_BP3.

 

Per TPS544C25RVFR DS, the power-on/reset Vout is set either by Rset when VSET is used or by EEPROM when VSET is not used.

Question:

1, For VSET is not used applications, does Ti have tools for EEPROM ISP programming? Does Ti have pre-programming service for out mass production?

2, For Rset value when VSET is used, are following VOUT values only supported options for boot-up? If not, what Rset value can set Vout to 0.82V?

3, Per above table, for 1.10V Vout, the Rset should be 121K 1%, why the WBDesign tools generated schematics and BOM use 133K 1%?

Thanks!

  • 0
    TI__Expert 7320 points

    Hi Jack,

    Our US team will review it and reply you by tomorrow.

  • 0
    TI__Expert 6846 points
    JDJ said:
    1, For VSET is not used applications, does Ti have tools for EEPROM ISP programming? Does Ti have pre-programming service for out mass production?

    We do not have a pre-programming service, but we provide software (Fusion Digital Power Designer: http://www.ti.com/tool/fusion_digital_power_designer) that enables storing configuration to NVM. To run the software, you will need a TI USB adapter which you can purchase at https://www.ti.com/tool/USB-TO-GPIO.

    JDJ said:

    2, For Rset value when VSET is used, are following VOUT values only supported options for boot-up? If not, what Rset value can set Vout to 0.82V?

    For instruction on how to set VOUT without using PMBUS, please refer to the following FAQ: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1023429/faq-tps544c25-how-to-set-vout-using-pin-strap-and-using-pmbus

  • 0 in reply to Tomoya Ide
    TI__Expert 3511 points

    For my third question, I am still unsure why the Vset resistor is being set. 

    Please see attached webench schematic. 

    Could you please let me know your thoughts? 

    Thanks,

    5224.Schematic.pdf

  • 0 in reply to JDJ
    TI__Expert 6846 points

    The only values allowed for VSET resistors are those listed in Table 2. Therefore, I believe this is a mistake on WEBENCH. I will ask them to get it fixed. 

  • 0 in reply to Tomoya Ide
    TI__Expert 3511 points

    We prefer to use the external HW circuit to set the default Vout at power-on/Reset. It would be more convenient for mass production although PCB re-spin is needed.

    I think if there is no any performance side effect per Rbase value change in external compensation circuit the workaround should be the default circuit design by our tools instead of using programmed value in EEPROM.

    Let me know if there is any performance side effect due to Rbase value change in external compensation circuit.

  • 0 in reply to JDJ
    TI__Expert 6846 points

    Adding a feedback resistor divider is likely no adverse performance side effect. You can use the Excel calculator (link below) to check your compensation circuit is stable.

    https://www.ti.com/lit/zip/slurb02

  • 0 in reply to Tomoya Ide
    TI__Expert 3511 points

    Couple more questions for TPS544C25.

    TSNS/SS pin is a multi-function pin for TPS544C25 – external Temp sensor input and/or soft-start detection. Per Option(MFR_SPECIFIC_21) register soft-start detection is the default function at power-on.

    Question:

    1. can I have a pull-down resistor, say 22.6K for 3ms soft-start, at this pin for power up soft-start control and also have external Cth + 3904 transistor for external temperature sense after during running time?
    2. If yes, will the 22.6K pull-down resistor affect the external temperature’s accuracy?
    3. The DS sheet says, 1nF is recommended for Cth, but the on-line WBDesign gave a 330pF for Cth, should I use 330pF or 1nF for Cth?

  • 0 in reply to JDJ
    TI__Expert 7320 points

    Hi Jack,

    Our US team will reply you by tomorrow.

  • 0 in reply to JDJ
    TI__Mastermind 33390 points

    Hello JDJ,

    1. Can I have a pull-down resistor, say 22.6K for 3ms soft-start, at this pin for power up soft-start control and also have external Cth + 3904 transistor for external temperature sense after during running time?
      I don't believe this is a good idea, a bias current is applied through internally that will draw current and measure the voltage on the TSNS/SS pin. This is described in Section 8.3.14 Over-Temperature Protection of the datasheet. With a resistor pulling to GND the ideality factor of the BJT may change from the perspective of the IC and what was the device was designed for. Measurement likely won't be as accurate.

      Why not set the soft-start turn-on through PMBus commands? The device by default uses the resistor for soft-start, but if you want to use the temperature measurement feature you would have to set SS_DET_DIS anyways. Otherwise this would always read 25C as mentioned in Section 8.6.51.8 SS_DET_DIS.

    2. If yes, will the 22.6K pull-down resistor affect the external temperature’s accuracy?
      Yes, it is likely that it would affect the external temperature accuracy. We would not be able to tell you exactly how much it would be affected by. This is outside the scope of what was characterized for the part.

    3. The DS sheet says, 1nF is recommended for Cth, but the on-line WBDesign gave a 330pF for Cth, should I use 330pF or 1nF for Cth?
      Use the datasheet's recommendation, in this case being 1-nF.  

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Expert 3511 points

    The reason why we can’t use SMBus to change the Vout to target level before power-on is we don’t have a power-on sequence controller. This DC-DC is for a rail which PMBus won’t be active until controller boots up. If do EEPROM pre-programming it would be not convenient for production. We understood the it can be either TSNS or SS.

    I will update my BOM to use 1nF for Cth.

  • 0 in reply to JDJ
    TI__Mastermind 33390 points

    I understand.

    Yes, the pin can be used for either TSNS or SS. We do not guarantee its usage for TSNS and SS at the same time however. By default this pin will be used for setting the soft-start time with temperature measurement disabled. Similarly, if the pin is configured for temperature measurement, the soft-start functionality is disabled. 

    As I mentioned I cannot say with certainty how accurate the temperature measurement would be with this resistance added, as this resistance could be pulling current during the pin's voltage measurement and this could potentially affect the resulting temperature reading.

    I would advice to test the device's temperature measurement with this resistance added and with it removed and confirm that the temperature is within the customer's acceptable design parameter ranges. We cannot guarantee this will work correctly however. 

    Good! The datasheet is the best source for finding the component values for the design.

    Let us know if you have any further questions.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Expert 3511 points

    This should meet 100ms PCIe bus enumeration timing requirement. If we have sufficient margin with TPS544C25’s default ~ 6ms SS time we will use this pin as TSNS for external temperature monitoring otherwise will load a 14.7K or 22.6K resistor at Cth instead of 1nF and DNI 2N3904 to set the tSS to 2ms or 3ms.

  • 0 in reply to JDJ
    TI__Mastermind 33390 points

    Ok perfect. 

    Best of luck in your design JDJ! That should be completely okay. Hopefully the default's 6-ms will be okay for your application.

    Best Regards,

    Luis Hernandez Salomo